Bearing temperature sensing apparatus for use on a trailer

ABSTRACT

An apparatus which incorporates a thermistor mounted in a stub axle being specially modified by the presence of an axial bore therein wherein the thermistor is positioned within the axle at a point between the bearing surfaces on the exterior thereof and further incorporating a conductor line which extends to an indicating apparatus located elsewhere. The indicating apparatus utilizes a DC power supply which is connected through a relay winding which reverses the operative status of relay contacts to form a visible indication of overheating of the bearings supported on the axle. Current flows from the source through the relay winding and thermistor to ground.

United States Patent [191 Williams BEARING TEMPERATURE SENSING APPARATUSFOR USE ON A TRAILER [76] Inventor: James G. Williams, 305 Chelsea Ln.,Friendswood, Tex. 77546 22 Filed: July 14,1972

21' Appl. No.: 271,919

[52] US. Cl 340/57, 340/269, 246/169 A [451 Feb. 12, 1974 PrimaryExaminer-Alvin H. Waring Attorney, Agent, or FirmDonald Gunn 57 ABSTRACTAn apparatus which incorporates a thermistor mounted in a stub axlebeing specially modified by the presence of an axial bore thereinwherein the thermistor is positioned within the axle at a point betweenthe bearing surfaces on the exterior thereof and further incorporating aconductor line which extends to an indicating apparatus locatedelsewhere. The indicating apparatus utilizes a DC power supply which isconnected through a relay winding which reverses the operative status ofrelay contacts to form a visible indication of overheating of thebearings supported on the axle. Current flows from the source throughthe relay winding and thermistor to ground.

10 Claims, 5 Drawing Figures BEARING TEMPERATURE SENSING APPARATUS FORUSE ON A TRAILER PRIOR ART US. Pat. Nos. 2,089,369; 2,961,875;2,187,958; 2,976,523; 2,420,968; 3,052,123; 2,429,817; 7 3,197,632;3,548,396.

BACKGROUND OF THE INVENTION A substantial industry has been developed inthe last few years in the manufacture of trailers used to haul campinggear, fold-out tent mechanisms, boats and the like. Such trailers arenot normally built with the structural strength, integrity andprotective devices normally found in larger and more expensive trailers.Their construction is normally adequate for their intended purposes butthey usually do not incorporate protection against many hazards ofoperation.

A significant hazard of operation in the use of a trailer is theoverheating of a wheel bearing. Normally, trailers incorporate a fixed'short stub axle which extends from a non-rotating member which issupported on the springs beneath the frame of the trailer. The axlereceives a pair of bearing assemblies thereon to support a hub which isboltedto a rim. Overheating of a bearing is extremely dangerous to theoperation of the trailer and towing vehicle. When a bearing becomesoverheated, normally the operator has little or no warning of thebearing failure. The operator will simply drive on until the bearingfailure becomes catastrophic. In such instances, the catastrophicfailure will be indicated by a blow out of the tire, visible smokeemerging from the bearing assembly, loss of a wheel, and so on. Suchcatastrophic failures are extremely hazardous to the owner and operator.Car wrecks on high speed highways have occurred because of bearingfailure in a trailer.

SUMMARY OF THE INVENTION The present invention incorporates equipmentwhich 'can modify a prexistent trailer, or be installed on a new trailerat the time of manufacture. It is intended for use with a trailer havingan axle connected by means of the typical spring arrangement beneath theframe of the trailer. The axle is non-rotative, and is connected nearits outer end to a fixed axle. The axle has a pair of bearing surfacesand is adapted to receive two sets of bearing assemblies. The bearingassemblies support a hub which is then bolted to a rim supporting atire. The present invention contemplates the drilling of an axialpassage through the axle to a point centered between the two bearingassemblies. A thermistor is positioned in the shaft. The thermistor isconnected by means of suitable conductors with an indicating circuit.One form of indicating circuit utilizes a series arrangementincorporating a DC supply, the winding of a relay, and a thermistorconnected to ground. The relay closes relay contact connected in serieswith an indicator light or audible alarm. The indicator light and relaycontact are also connected from the source to ground. When.

the thermistor senses a rise in temperature, its resistance drops andthe change in resistance increases the current flow through the relay.The relay is thus operated, closing the contacts and forming a visibleindication. Depending on the range of thermistor selected, differenttemperature alarm levels can be obtained.

Typically, anindicating level of about is used which prevents damage tothe wheel and trailer.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view through astub axle which has been modified to cooperate with the presentinvention;

FIG. 2 is a sectional view through a trailer modified to incorporate thetemperature protection system of the present invention and utilizing themodified stub axle of FIG. 1;

FIG. 3 illustrates a first alarm indication circuit;

FIG. 4 indicates a second or alternative alarm indication circuit meansfor use with the present invention; and,

FIG. 5 represents the preferred embodiment of alarm indicating circuitryfor use with the presentinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Attention is first directed toFIG. 2 of the drawings where the numeral 10 identifies a trailer of thetype specified for use with the present invention. The trailer 10 hasbeen modified to incorporate the present invention which is indicatedgenerally by the numeral 12. The protection system of the presentinvention incorporates additional apparatus not shown in FIG. 2 butwhich will be described hereinafter. The trailer 10 incorporates a framemember 14 connected in the customary manner to an elongate leaf spring16. From the center of the spring, a shackle 18 extends around a fixedaxle 20. The axle 20 spans the width of the trailer and transfer theweight of the trailer and its load to the wheels. As will be understood,the springs 16 are positioned on both sides of the trailer to cushionand stablize the trailer and its load.

The fixed axle 20 extends outwardly toward the side of the trailer andsupports an upright plate 22. A gusset 24 assists in positioning andreinforcing the upright plate 22. The plate 22 is joined, by welding, toa stub axle 26. One such axle is shown in FIG. 1 in enlarged view,specially modified to incorporate the present invention.

Attention is momentarily directed to FIG. 1 of the drawings. The stubaxle is a nonrotating axle. It is relatively short in length,approximating perhaps eight to fifteen inches. It can be longer when atandem arrangement is contemplated. The stub axle shown in FIG. 1 isintended for use with a single wheel. The stub axle incorporates asubstantial thick portion at 28 which has the maximum diameter. Thenumeral 30 identifies a first bearing flat while the numeral 32identifies a second bearing flat. These flats are perfectly concentricand circular about the body of the axle 26. They are spaced from oneanother and separated by a tapered surface 34. The tapered surface spansa few inches between the bearings flats 30 and 32. It will be observedthat the specimen of stub axle shown in FIG. 1 tapers to a smallerdiameter at the bearing flat 32. Some short fixed non-rotative stubaxles incorporate bearing surfaces 30 and 32 which are equal in diameterand in that event, the surface 34 is cylindrical, not tapered. FIG. 1illustrates the more common and popular version of stub axle wherein ataper is found between the two bearing flats.

The outer end of the stub axle is threaded at 36 to receive a crown nutas will be described. For incorporation in the present invention, anaxial hole 40 is drilled into the stub axle. The passage 40 extendsinboard, past both bearing surfaces. A radially outwardly directed hole42 intercepts the axial passage. It is preferably to center the axialpassage where it passes through the bearing surfaces.

The modifications contemplated for the present invention provide apassage means whereby a thermistor is positioned approximatelyequidistant between the two bearing surfaces 30 and 32. Moreover, theradial passage 42 serves as a port from which electrical wires emergefor connection with the remainder of the equipment on the vehicle. Thelateral or radial passage 42 is sufficiently inboard to clear all theassemblies associated with the bearing and hub as will be described.This is more clearly shown in FIG. 2.

Returning to FIG. 2, a first bearing assembly indicated by the numeral46 is positioned about the bearing surface 30. A second bearing assembly48 is positioned about the smaller bearing surface. The two bearingassemblies 46 and 48 support a hub 50. The hub 50 has an internal axialpassage contoured to rest on the two bearing assemblies as shown in FIG.2. The hub 50 is locked in position by means of a crown nut 52 which isthreaded on the outer end of the fixed shaft 26. Preferably, a cotterpin is passed through the grooves in the crown nut and through a holedrilled perpendicular to the passage 40 previously described. Thissecures the bearing assemblies 46 and 48 in position and supports thehub 50 at the proper location. It will be observed that the hub 50rotates on the bearing assemblies about the shaft 26 functioning as anaxle.

An external flange 52 extends from the hub. The flange 52 is suitablefor connection to a rim 54. The rim 54 is joined to the hub 52 by meansof lug bolts 56. A ring of typically four to six lug bolts is used tosecure the rim to the hub. The rim 54 has a pair of external beads whichsupport and position a tire about the rim.

The numeral 60 identifies a thermistor which is placed in the axialpassage 40. The thermistor is preferably only slightly smaller than theaxial passage, and is preferably held inposition by means of epoxy orother filling material which is inserted from either end to fix thethermistor 60 in position. The thermistor 60 is connected to a pair ofconductors 62 which lead to additional circuitry as will be described.The thermistor 60 is preferably positioned at a mid-point between thetwo bearing assemblies 46 and 48. It will be appreciated that eitherbearing may wear out first. When either of the bearings becomes worn,unlubricated or otherwise operated in less than optimum circumstances,the amount of heat generated in the bearing from the friction ofrotation increases. The heat is conducted into the various metallicparts in contact with the bearings. Of course, some of the heat isconducted into the hub 50. However, a substantial amount of heat isconducted into the shaft 26 which supports the entire wheel assembly. Asthe heat is transferred into the shaft, the temperature in thethermistor is elevated. The thermistor responds to the increase intemperature to form an electrical signal in the manner to be describedwhich is used to sound an alarm, indicating imminent bearing failure.The position of the thermistor 60 is so calculated to form an alarm, inconjunction with the apparatus to be described, that alerts the drivesufficiently rapidly to avoid the occurrance of damage to the bearingassemblies and the wheel.

Attention is next directed to FIG. 3 of the drawings which illustrates arather simplified but highly successful electronic means for use withthe present invention. The numeral 60 identifies the thermistorschematically included in the circuitry. The numeral 64 identifies a DCvoltage source which can be the automotive electrical system normallyfound on a vehicle. The numeral 66 identifies a series lamp which is inseries with the thermistor 60 which is grounded at one side. When thethermistor 60 is cool, the drop across the lamp 66 is so small as to notilluminate the lamp. For instance, the thermistor might have a nominalresistance of about 100 to 1,000 ohms. However, when the thermistor 60is heated to a selected temperature level, the terminal resistance mightdrop as low as about 5 ohms. This drop enables additional current toflow through the lamp 66. As the current flow increases, the lampapproaches incandescance and glows in a manner to be seen or observed.Preferably, the lamp 66 is installed in the towing vehicle at such alocation to enable the operator to see the lamp. It is installed by theuse ofa long wire and plug and socket. A test switch 68 momentarilyshorts the lamp to ground to thereby enable the operator to test thelamp.

The circuitry shown in FIG. 3 is adapted for use with a single wheel.The circuitry shown and illustrated in FIG. 4 is similar to that of FIG.3, but is adapted to be used with several trailer wheels. Theillustration incorporates eight individual thermistors although thisnumber can clearly be increased or decreased with impunity. In FIG. 4,the numeral 70 identifies a voltage source which again can be theautomotive electrical system. An ammeter 72 is connected in parallel toa number of switches 74, each of which is connected in series with asingle thermistor. The thermistors are all grounded at one side.

For a given wheel, current flows from the source 70 through the ammeter72, the switch 74 and the series thermistor 60 to ground. Again, whenthe thermistor is heated, its terminal resistance drops and the flowthrough the ammeter 72 increases. Preferably, the ammeter 72 iscalibrated, not in current flow, but in degrees Fahrenheit to indicatedthe bearing temperature. It will be observed that several thermistorsare connected in parallel and in the event that two or more switches areclosed an increased current flow through the meter movement 72 will beobserved. The switches 74 can be used in any desired manner. One mannerof operation is to periodically close each switch 74 to obtain a visualindication of the temperature of the thermistor sensing deviceassociated with a particular wheel. This can be expedited through theuse of a rotary switch as opposed to single pole, single throw switchesas illustrated in FIG. 4. The rotary switch should be operatedperiodically through all of the positions to test all of the wheelswhich are protected by the present invention.

A more expensive apparatus is shown in FIG. 5 of the drawings. A voltagesource is connected to an additional ammeter movement 82. DC power isapplied directly to a conductor 84. The conductor 84 communicates with asingle lamp 86 in series with a relay contact 88 which is then grounded.The conductor 84 also communicates through the winding 90 of the relaywhich then is communicated with a switch 92 and a thermistor 60 which isgrounded.

The arrangement of FIG. 5 is illustrated for fourwheel protection.Again, the number can be increased or decreased. Each wheel has its ownalarm system which is continuously monitored in contrast with thearrangement with FIG. 4. The operation of the circuitry of of FIG. 5 isas follows. When the thermistor 60 becomes heated, current flows throughit is increased. This increasein current flow is sensed by a coil 90comprising a portion of a relay. The coil 90 closes the relay contacts88. When these'contacts are closed, the lamp 86 is illuminated formingan alarm signal. The alarm signal occurs when the current flow throughthe coil 90 becomes sufficient to be associated with an overheatedbearing assembly. Should the operator desire, he can momentarily closethe switch 92. This then directs the current flow through the ammeter82. When this occurs, he can then obtain an indication on the ammetercalibrated in degrees of temperature of the actual temperature. Thiswill then govern his emergency actions. For instance, as he is only ashort distance from his destination, and the temperature indicated isnot relatively high, he can then drive on. If he determines that he hasan overheated bearing and there are too many miles to travel beforeemergency assistance can be obtained, he can pull to the side of theroad and let the bearing assembly cool. The indication on the ammeter 82can be used to determine the advisability of splashing cool water on theentire wheel assembly if service is unavailable.

The arrangement of FIG. 5 is particularly adapted for use with afour-wheel trailer. Each indication is formed independently of the otherwheels. With the switch 92 in the position illustrated, each alarmsignal is formed independently. In theory, all four alarm signals canoccur simultaneously.

The indicating apparatus shown in FIG. 5 is the more expensive and mostsophisticated arrangement. It is particularly advantageous for larger ormore expensive trailers and trailer pay loads.

The foregoing is directed to the preferred embodiment of the presentinvention. Numerous alterations in the present invention may beincorporated. By way of example and not limitation, the presentinvention is adapted for installation on a fixed, non-rotating axlesupporting a single wheel or dual wheels. It can be used on fixed,non-rotating axles where the bearings are of different sizes, or areequal in size.

The scope of the present invention is determined by the claims which areappended hereto.

I claim:

I. For use with a non-rotating axle supporting a trailer frame memberwherein the axle has a first bearing surface thereabout and an extendedportion of a cylindrical shape extending to a second bearing surfacethereabout wherein the axle supports two bearing assemblies on thebearing surfaces which support a hub for rotation about the axle withthe hub adapted to be an indicator means connected to said sensing meansfor forming an indication of. temperatures in said axle above apredetermined level,

and the vehicle has at least two axles similarly protected by saidsensor means connected to a common indicator means, therebeing a relaycoil connected in series with each of said sensing means, a switch meansclosed by said relay coil on flowing a current above a predeterminedlevel through said relay coil, a lamp connected in series with saidswitch means, a voltage source connected to said series connected lampand switch means for applying power to said lamp when said switch meansis closed but not when said switch means is open.

2. The structure of claim I wherein said sensing means includes athermistor.

3. The structure of claim 1 including a switch means connected to saidsensing means.

4. The structure of claim 1 wherein a plurality of axles have similarlyarranged sensing means and all such sensing means are connected to acommon indicator means, therebeing a switch means connected in serieswith each of said sensing means, and wherein said indicating means formsan indication dependent on the signal applied thereto by operation ofsaid switch means.

5. The structure of claim 1 including a meter movement connectedselectively to certain of said sensing means.

6. The structure of claim 5 wherein said meter movement is calibrated toindicate temperature.

7. The structure of claim I including a common voltage source for saidsensing means.

8. The structure of claim I wherein said passage means is formed axiallyof said axle, and connects with a radially directed passage openinginboard of said first bearing surface and said conductor extends fromsaid axle to a common location with conductors from other such axles andare connected to said indicating means at a location within view of anoperator of a vehicle pulling the trailer frame.

9. The structure of claim 8 wherein said indicating means forms avisible and an audible indication.

10. The structure of claim I wherein said passage means is formedaxially of said axle, and connects with a radially directed passageopening inborad of said first bearing surface.

1. For use with a non-rotating axle supporting a trailer frame memberwherein the axle has a first bearing surface thereabout and an extendedportion of a cylindrical shape extending to a second bearing surfacethereabout wherein the axle supports two bearing assemblies on thebearing surfaces which support a hub for rotation about the axle withthe hub adapted to be releasably connected to a rim and tire mounted onthe rim, the improvement comprising a passage means formed in said axleextending to a point in said axle between said first and second bearingsurfaces, temperature sensing means in said passage means responsive toan increase of temperature in said axle as a result of overheating thebearing assemblies, an output signal conductor from said sensing means,an indicator means connected to said sensing means for forming anindication of temperatures in said axle above a predetermined level, andthe vehicle has at least two axles similarly protected by said sensormeans connected to a common indicator means, therebeing a relay coilconnected in series with each of said sensing means, a switch meansclosed by said relay coil on flowing a current above a predeterminedlevel through said relay coil, a lamp connected in series with saidswitch means, a voltage source connected to said series connected lampand switch means for applying power to said lamp when said switch meansis closed but not when said switch means is open.
 2. The structure ofclaim 1 wherein said sensing means includes a thermistor.
 3. Thestructure of claim 1 including a switch means connected to said sensingmeans.
 4. The structure of claim 1 wherein a plurality of axles havesimilarly arranged sensing means and all such sensing means areconnected to a common indicator means, therebeing a switch meansconnected in series with each of said sensing means, and wherein saidindicating means forms an indication dependent on the signal appliedthereto by operation of said switch means.
 5. The structure of claim 1including a meter movement connected selectively to certain of saidsensing means.
 6. The structure of claim 5 wherein said meter movementis calibrated to indicate temperature.
 7. The structure of claim 1including a common voltage source for said sensing means.
 8. Thestructure of claim 1 wherein said passage means is formed axially ofsaid axle, and connects with a radially directed passage opening inboardof said first bearing surface and said conductor extends from said axleto a common location with conductors from other such axles and areconnected to said indicating means at a location within view of anoperator of a vehicle pulling the trailer frame.
 9. The strucTure ofclaim 8 wherein said indicating means forms a visible and an audibleindication.
 10. The structure of claim 1 wherein said passage means isformed axially of said axle, and connects with a radially directedpassage opening inborad of said first bearing surface.